Photo detector device, photo sensor and spectrum sensor

ABSTRACT

A photodetector device includes: a first semiconductor region of a first conductivity type electrically connected to a first external electrode: a second semiconductor region of a second conductivity type formed on the first semiconductor region; a third semiconductor region of the first conductivity type formed on the second semiconductor region; and a plurality of fourth semiconductor regions of the second conductivity type formed on the second semiconductor region, each of the plurality of fourth semiconductor regions being surrounded by the third semiconductor region, including a second conductivity type impurity having a concentration higher than a concentration of the second semiconductor region, and electrically connected to a second external electrode.

BACKGROUND

The entire disclosure of Japanese Patent Application No. 2010-075008,filed Mar. 29, 2010 is expressly incorporated by reference herein.

1. Technical Field

The invention relates to photodetector devices, photo sensors andspectrum sensors.

2. Related Art

A known photodetector device is composed of a photodiode having a firstsemiconductor region of a first conductivity type (for example, N type)formed on a substrate, and a second semiconductor region of a secondconductivity type (for example, P type) formed on the firstsemiconductor region.

For example, Japanese patent 3584196 (see claim 1, FIGS. 1, 5 and 11,and Paragraph 0062) (Patent Document) describes a photodetector devicehaving (1) a first semiconductor region of a first conductivity type,(2) a second semiconductor region of a second conductivity type arrangedon the first semiconductor region, (3) a third semiconductor region ofthe first conductivity type arranged on the surface of the secondsemiconductor region, (4) an electrode region of the second conductivitytype that is arranged on the surface of the second semiconductor regionand connected to an anode or a cathode, wherein the third semiconductorregion is formed in a manner to surround the periphery of the electroderegion, and the electrode region has an impurity concentration higherthan that of the second semiconductor region. According to the PatentDocument, the impurity concentration of the third semiconductor regionis made higher than the impurity concentration of the secondsemiconductor region, whereby the capacitance of the photodetectorsection is lowered.

However, in the photodetector device described in the Patent Document,because the impurity concentration of the electrode region is madehigher than the impurity concentration of the second semiconductorregion, and the impurity concentration of the third semiconductor regionis made higher than the impurity concentration of the secondsemiconductor region, the impurity concentration of the secondsemiconductor region has to be made relatively low. On the other hand,in order for carriers (electrons or holes) generated by thephotoelectric effect in the second semiconductor region of the secondconductivity type that forms a PN junction with the first semiconductorregion of the first conductivity type to move into the electrode regionof the second conductivity type, the carriers need to move within thesecond semiconductor region of the second conductivity type. When theimpurity concentration of the second semiconductor region is lowered, asdescribed in the Patent Document, the electrical resistance of thesecond semiconductor region becomes higher.

SUMMARY

An aspect of the invention pertains to a technology for effectivelymoving carriers (electrons or holes) generated in the secondsemiconductor region to a semiconductor region with high impurityconcentration connected to an external electrode.

In accordance with an embodiment of the invention, a photodetectordevice includes a first semiconductor region of a first conductivitytype electrically connected to a first external electrode, a secondsemiconductor region of a second conductivity type formed on the firstsemiconductor region, a third semiconductor region of the firstconductivity type formed on the second semiconductor region, and aplurality of fourth semiconductor regions of the second conductivitytype formed on the second semiconductor region, each of the plurality offourth semiconductor regions being surrounded by the third semiconductorregion, each of the plurality of fourth semiconductor regions includinga second conductivity type impurity having a concentration higher thanthat of the second semiconductor region, and electrically connected to asecond external electrode. According to the embodiment set forth above,the fourth semiconductor regions connected to the second externalelectrode are formed in plurality on the second semiconductor region,such that carriers in the second semiconductor region only need tomigrate in a small distance, and thus the carriers can be effectivelymoved to the fourth semiconductor region.

In accordance with an aspect of the embodiment described above, thethird semiconductor region may preferably be electrically connected to athird external electrode. Accordingly, by applying a predeterminedvoltage to the third semiconductor region, a sufficient depletion layercan be formed in the second semiconductor region formed below the thirdsemiconductor region.

In accordance with an another embodiment of the invention, aphotodetector device includes a first semiconductor region of a firstconductivity type electrically connected to a first external electrode,a second semiconductor region of a second conductivity type formed onthe first semiconductor region, a third semiconductor region of thesecond conductivity type formed on the second semiconductor region,including a second conductivity type impurity having a higherconcentration than that of the second semiconductor region, andelectrically connected to a second external electrode, and a pluralityof fourth semiconductor regions of the first conductivity type formed onthe second semiconductor region, each of the plurality of fourthsemiconductor regions being surrounded by the third semiconductorregion. According to the embodiment set forth above, the thirdsemiconductor region connected to the second external electrode isformed on the second semiconductor region and surrounds the forthsemiconductor region, such that carriers in the second semiconductorregion need to migrate only in a small distance, and thus the carrierscan be effectively moved with respect to the third semiconductor region.

In accordance with an aspect of the embodiment described above, each ofthe plurality of fourth semiconductor regions may preferably beelectrically connected to the third external electrode. According tothis composition, by applying a predetermined voltage to the pluralityof fourth semiconductor regions, a sufficient depletion layer can beformed in the second semiconductor region formed below the fourthsemiconductor regions.

In accordance with an aspect of the embodiment described above, thethird external electrode may preferably be a common electrode shared bythe first external electrode. Accordingly, the first external electrodeconnected to the first semiconductor region and the third externalelectrode connected to the third semiconductor region or the fourthsemiconductor region can be commonized, such that the circuit structurecan be simplified.

In accordance with still another embodiment of the invention, aphotosensor includes the photodetector device described above, and anangle restriction filter that restricts an incident angle of lightpassing therein toward the photodetector device. In an aspect, at leastone portion of the angle restriction filter is formed from a conductivematerial, and each of the plurality of fourth semiconductor regions ofthe photodetector device is connected to the second external electrodethrough the one portion of the angle restriction filter. According tothis embodiment, electrical connection between the fourth semiconductorregion surrounded by the third semiconductor region and the secondexternal electrode is made by the angle restriction filter, such thatadditional components for wiring are not necessary, and therefore areduction in the amount of receiving light by wirings can be suppressed.

In accordance with yet another embodiment of the invention, aphotosensor includes the photodetector device described above, and anangle restriction filter that restricts an incident angle of lightpassing therein toward the photodetector device. In an aspect, at leastone portion of the angle restriction filter is formed from a conductivematerial, and each of the plurality of fourth semiconductor regions ofthe photodetector device is connected to the third external electrodethrough the one portion of the angle restriction filter. According tothis embodiment, electrical connection between the fourth semiconductorregion surrounded by the third semiconductor region and the thirdexternal electrode are made by the angle restriction filter, such thatadditional components for wiring are not necessary, and therefore areduction in the amount of receiving light by wirings can be suppressed.

In accordance with a further embodiment of the invention, a photosensorincludes the photodetector device described above, an angle restrictionfilter that restricts an incident angle of light passing therein towardthe photodetector device, and a wavelength restriction filter thatrestricts wavelengths of light that can pass through the anglerestriction filter. According to this embodiment, the photodetectordevice described above is used, such that carriers in the secondsemiconductor region have to move only in a short distance, andtherefore the carriers can be effectively moved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a see-through plan view of a photodetector device and aspectrum sensor in accordance with a first embodiment of the invention.

FIG. 2 is a cross-sectional view taken along lines II-II of FIG. 1.

FIGS. 3A-3E are views showing steps of forming the photodetector device.

FIG. 4 is see-through plan view of a photodetector device and a spectrumsensor in accordance with a second embodiment of the invention.

FIG. 5 is a cross-sectional view taken along lines V-V of FIG. 4.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Preferred embodiments of the invention are described in detail below. Itis noted, however, that the embodiments described below do not undulylimit the contents of the invention set forth in the scope of patentclaims. Also, not all of the compositions described in the embodimentswould necessarily be essential for the solution provided by theinvention. Furthermore, the same components will be appended with thesame reference numbers, and their description will not be repeated.

1. First Embodiment

FIG. 1 is a see-through plan view of a photodetector device and aspectrum sensor 1 in accordance with a first embodiment of theinvention, and FIG. 2 is a cross-sectional view taken along lines II-IIof FIG. 1. The spectrum sensor 1 includes an angle restriction filter10, a wavelength restriction filter 20, and a photodetector device 30(see FIG. 2). In FIG. 1, illustration of the wavelength restrictionfilter 20 is omitted.

In a silicon substrate 3 that serves as a semiconductor substrate wherethe spectrum sensor 1 is formed, an unshown electronic circuit is formedfor applying a predetermined reverse bias voltage to the photodetectordevice 30, detecting a current based on photovoltaic power generated atthe photodetector device 30, amplifying an analog signal according tothe magnitude of the current, converting the analog signal to a digitalsignal and the like. A plurality of aluminum (Al) alloy layers forwiring (not shown) are connected to semiconductor elements composing theelectronic circuit, thereby providing electrical connections among thesemiconductor elements composing the electronic circuit, and electricalconnections between the electronic circuit and external components.

Conductive plugs (not shown) are connected between the plurality ofaluminum alloy layers. The conductive plugs electrically connectadjacent upper and lower ones of the aluminum alloy layers at placeswhere the conductive plugs are provided.

1-1. Angle Restriction Filter

As shown in FIG. 2, the angle restriction filter 10 is formed on thesilicon substrate 3 in which the photodetector device 30 is formed. Inthe angle restriction filter 10 of the present embodiment, light shieldmembers 13 composed of conductive plugs that are formed by the sameprocess used for the conductive plugs on the above-described electroniccircuit, thereby forming optical path wall sections. The light shieldmembers 13 are formed from tungsten (W).

Further, the silicon substrate 3 is provided thereon with a plurality ofaluminum alloy layers 11 formed by the same multilayer wiring processused for the aluminum alloy layers on the electronic circuit describedabove, which are laminated through silicon oxide (SiO₂) layers 12serving as insulation layers each having light transmissivity (in otherwords, light transmissivity to light having wavelengths to be receivedby the photodetector device 30). The embodiment is not limited to thealuminum alloy layers, and the layers 11 may be composed of copper (Cu)alloy layers.

The light shield members 13 are composed of material that does notsubstantially transmit light with wavelengths to be received by thephotodetector device 30, and may be continuously formed in a pluralityof layers (see FIG. 2) in a predetermined pattern, for example, alattice configuration (see FIG. 1) on the silicon substrate 3, such thatan optical path in the lamination direction of the light shield members13 is formed.

The incident angle of light passing through the optical path isrestricted by the optical path wall sections formed with the lightshield members 13. More specifically, when light incident upon theoptical path is angled more than a predetermined restriction angle withrespect to the direction of the optical path, the light hits the lightshield members 13, whereby a portion of the light is absorbed by thelight shield members 13, and the remaining portion is reflected. Thereflection is repeated until the light passes the optical path, wherebythe reflected light becomes weaker. Therefore, light that can pass theangle restriction filter 10 is restricted to those light having incidentangles with respect to the optical path being less than thepredetermined restriction angle.

Areas surrounded by the light shield members 13 are composed of theabove-described silicon oxide layer 12 having light transmissivity, andthus function as light transmission sections that transmit incidentlight.

In the embodiment described above, the light shield members 13 areformed in multiple layers in a predetermined lattice pattern on thesilicon substrate 3, thereby forming the optical path wall sections.Therefore, very fine patterns can be formed, and the restriction filters10 can be manufactured in a small size. Further, compared to a spectrumsensor that is formed by laminating members, the manufacturing processcan be simplified, and a reduction in transmission light by adhesive canbe suppressed.

In accordance with a preferred embodiment, the light shield members 13are formed from the same material (tungsten, or the like) as that of theconduction plugs described above. By this, the angle restriction filter10 can be formed by the semiconductor process at the same time when thealuminum alloy layers for wirings for the electronic circuits and theconductive plugs are formed on the same silicon substrate 3.

Further, in accordance with a preferred embodiment, a titanium nitride(TiN) film 14 that serves as an adhesive layer between tungsten andsilicon oxide is formed on the surface of each of the light shieldmembers 13.

Also, in accordance with a preferred embodiment, the light shieldmembers 13 are electrically connected to the aluminum alloy layers 11through side surfaces of the aluminum alloy layers 11. As fourthsemiconductor regions 34 (to be described below) to be formed on thesilicon substrate 3 are electrically connected to the bottom ends of thelight shield members 13, electrical connection between the photodiodedevice 30 and the aluminum alloy layers 11 can be achieved.

1-2. Wavelength Restriction Filter

The wavelength restriction filter 20 is formed on the angle restrictionfilter 10, and is composed of a plurality of laminated layers of thinfilms of a low refractive index 21 such as silicon oxide (SiO₂) and thinfilms of a high refractive index 22 such as titanium oxide (TiO₂), whichare slightly tilted with respect to the silicon substrate 3. The thinfilms of a low refractive index 21 and the thin films of a highrefractive index 22 each having a predetermined film thickness on theorder of, for example, submicron, are laminated, for example, in about60 layers in total, thereby forming, for example, a thickness of about 6μm on the whole.

Tilt angles θ₁ and θ₂ of the low refractive index thin films 21 and thehigh refractive index thin films 22 with respect to the siliconsubstrate 3, may be set at, for example, 0 degree or greater but 30degrees or smaller, according to set wavelengths of light to be receivedby the photodetector device 30.

In order to have the low refractive index thin films 21 and the highrefractive index thin films 22 tilted with respect to the siliconsubstrate 3, for example, a tilt structure 23 having transmissivity isformed on the angle restriction filter 10, and the low refractive indexthin films 21 and the high refractive index thin films 22 are formed onthe tilt structure 23. The tilt structure 23 may be formed by, forexample, depositing a silicon oxide layer on the angle restrictionfilter 10 and processing the silicon oxide layer by a CMP (chemicalmechanical polishing) method.

In this manner, by forming in advance the tilt structures 23 having thetilt angles θ₁ and θ₂ that are different depending on the setwavelengths of light to be received by the photodetector device 30, thelow refractive index thin films 21 and the high refractive index thinfilms 22 can be formed each in the same thickness by a common process,without regard to the set wavelengths of light to be received by thephotodetector device 30.

The wavelength restriction filter 20 having such a structure describedabove restricts wavelengths of light (light that can pass through theangle restriction filter 10) incident on the angle restriction filter 10within the predetermined range of restricting angles. More specifically,a portion of incident light that has entered the wavelength restrictionfilter 20 becomes reflected light and another portion thereof becomestransmitting light at an interface between a set of the low refractiveindex thin film 21 and the high refractive index thin film 22. Then, aportion of the reflected light reflects again at an interface betweenanother set of the low refractive index thin film 21 and the highrefractive index thin film 22 and the aforementioned transmitting lightare coupled together. In this instance, when light has a wavelength thatmatches with the optical path length of reflected light, the reflectedlight and the transmitting light match in phase with each other, andthus strengthen each other. When light has a wavelength that does notmatch with the optical path length of reflected light, the reflectedlight and the transmitting light do not match in phase with each other,and thus weaken each other (destructively interfere with each other).

The optical path length of reflected light is determined by the tiltangles of the low refractive index thin film 21 and the high refractiveindex thin film 22 with respect to the direction of the incident light.Accordingly, when the interference action described above is repeated inthe low refractive index thin films 21 and the high refractive indexthin films 22, which amount to the total of sixty layers, light havingonly specific wavelengths can pass the wavelength restriction filter 20,according to the incident angle of incident light, and are emitted fromthe wavelength filter 20 at a predetermined emission angle (for example,at the same angle as the incident angle to the wavelength restrictionfilter 20).

The angle restriction filter 10 allows only light incident on the anglerestriction filter 10 in the predetermined range of restriction anglesto pass therein. Accordingly, the wavelengths of light that passesthrough the wavelength restriction filter 20 and the angle restrictionfilter 10 are restricted to a predetermined range of wavelengths whichis determined by the tilt angles θ₁ and θ₂ of the low refractive indexthin films 21 and the high refractive index thin films 22 with respectto the silicon substrate 3, and the range of restriction angles ofincident light the angle restriction filter 10 allows to pass.

1-3. Photodetector Device

The photodetector device 30 is an element that receives light that haspassed through the wavelength restriction filter 20 and the anglerestriction filter 10, and converts the light to photovoltaic power.FIG. 2 shows the photodetector device 30 that receives light withwavelengths that are determined by the tilt angle θ₁ of the wavelengthrestriction filter 20, and a portion of the photodetector device 30 thatreceives light with wavelengths that are determined by the tilt angle θ₂of the wavelength restriction filter 20.

The photodetector device 30 includes various kinds of semiconductorregions that are formed in the silicon substrate 3 by ion implantationor the like. In accordance with the present embodiment, thesemiconductor regions formed in the silicon substrate 3 include: (1) afirst semiconductor region 31 of a first conductivity type electricallyconnected to a first external electrode; (2) a second semiconductorregion 32 of a second conductivity type formed on the firstsemiconductor region 31; (3) a third semiconductor region (a pinninglayer) 33 of the first conductivity type formed on the secondsemiconductor region 32; (4) a plurality of fourth semiconductor regions34 of the second conductivity type formed on the second semiconductorregion 32, each of the plurality of fourth semiconductor regions 34being surrounded by the third semiconductor region 33, each of theplurality of fourth semiconductor regions 34 including a secondconductivity type impurity having a higher concentration than that ofthe second semiconductor region 32, and electrically connected to asecond external electrode.

In this embodiment, the first conductivity type is, for example, N type,and the second conductivity type and the conductivity type of thesilicon substrate 3 are, for example, P type. In this case, the firstexternal electrode is a cathode electrode, and the second externalelectrode is an anode electrode.

The first semiconductor region 31 is connected to a connection section37 to the first external electrode through a fifth semiconductor region35 of the first conductivity type. On the other hand, the secondsemiconductor region 32 is connected to connection sections 38 to thesecond external electrode through the plurality of fourth semiconductorregions 34. Therefore, a reverse bias voltage can be applied to the PNjunction formed between the first semiconductor region 31 and the secondsemiconductor region 32 through the first external electrode and thesecond external electrode.

As light that has passed through the angle restriction filter 10 isreceived by the photodetector device 30, photovoltaic power is generatedat the PN junction formed between the first semiconductor region 31 andthe second semiconductor region 32, whereby an electrical current isgenerated. By detecting the electrical current by the above-describedelectronic circuit connected to the first external electrode or thesecond external electrode, the light received by the photodetectordevice 30 can be detected.

In the first embodiment, the fourth semiconductor region 34 of thesecond conductivity type is formed, surrounded by the thirdsemiconductor regions (pinning layer) 33 of the first conductivity type(see FIG. 1), such that a large area for the third semiconductor regions33 can be secured on the second semiconductor region 32. Accordingly,generation of thermally excited carriers at the interface between thesilicon substrate 3 and the silicon oxide layer 12 and generation ofdark current noise caused by the thermally excited carriers can besuppressed.

Moreover, in accordance with the first embodiment, as the fourthsemiconductor regions 34 each connected to the second external electrodeand surrounded by the third semiconductor region 33 are formed inplurality (see FIG. 1), the distance in which carriers generated in thesecond semiconductor region 32 that is located below the thirdsemiconductor region 33 moves to the fourth semiconductor region 34 canbe shortened, such that the carriers are effectively moved.

Also, in accordance with the first embodiment, the third semiconductorregion 33 is connected to the connection section 39 connecting to thethird external electrode through the fifth semiconductor region 35. Inthe present embodiment, as shown in FIG. 2, the connection section 37 tothe first external electrode and the connection section 39 to the thirdexternal electrode are commonized, such that the first externalelectrode and the third external electrode are a commonly sharedelectrode. By this structure, a voltage equivalent to theabove-described reverse bias voltage applied to the first externalelectrode can be applied to the third semiconductor region 33, such thata sufficient depletion layer can be formed in the second semiconductorregion 32. In this exemplary embodiment, the first semiconductor region31 and the third semiconductor region 33 are connected at the fifthsemiconductor region 35. However, without any particular limitation tothe above, the first semiconductor region 31 may be connected to thefirst external electrode by a conductive layer (not shown) that is notconnected to the third semiconductor region 33, and the first externalelectrode and the third external electrode may be set at differentpotentials in the same polarity.

Also, in the embodiment described above, the angle restriction filter 10is formed from a conductive material. Further, the plural fourthsemiconductor regions 34 are connected to the connection sections 38that are located at the lower ends of the angle restriction filters 10,respectively, and are connected to the second external electrode throughthe angle restriction filters 10. Accordingly, it is not necessary toprovide conductive members for wiring other than the angle restrictionfilter 10 on the photodetector device 30, and therefore a reduction inthe amount of receiving light by such wirings can be avoided.

1-4. Manufacturing Method in accordance with First Embodiment

Here, a method for manufacturing the spectrum sensor 1 in accordancewith the first embodiment will be briefly described. The spectrum sensor1 is manufactured through initially forming the photodetector device 30on the silicon substrate 3, then forming the angle restriction filter 10on the photodetector device 30, and then forming the wavelengthrestriction filter 20 on the angle restriction filter 10.

Initially, the photodetector device 30 is formed on the siliconsubstrate 3. FIGS. 3A-3E are views showing a process of forming thephotodetector device 30.

(1) First, a patterned resist (not shown) is formed, and a firstsemiconductor region 31 of N type is formed in the P type siliconsubstrate 3 by ion injection or the like, using the resist as a mask, asshown in FIG. 3A. The ions to be injected may be, for example, phosphor(P⁺), the ion injection energy may be, for example, 1 MeV-3 MeV, and thedoping amount may be, for example, 1.0×10¹² atoms/cm²-1.0×10¹⁴atoms/cm². After the ion injection, the resist is removed.

(2) Then, as shown in FIG. 3B, a patterned resist R2 is formed, and afifth semiconductor region 35 of N type is formed by further injectingions in the first semiconductor region 31, using the resist R2 as amask. The ions to be injected may be, for example, phosphor (P⁺), theion injection energy may be, for example, 100 KeV-1000 KeV, and thedoping amount may be, for example, 1.0×10¹³ atoms/cm²-1.0×10¹⁵atoms/cm². After the ion injection, the resist R2 is removed.

(3) Then, as shown in FIG. 3C, a patterned resist R3 is formed, and asecond semiconductor region 32 of P type is formed by further injectingions in the first semiconductor region 31, using the resist R3 as amask. The ions to be injected may be, for example, boron (B⁺), the ioninjection energy may be, for example, 50 KeV-300 KeV, and the dopingamount may be, for example, 1.0×10¹¹ atoms/cm²-1.0×10¹³ atoms/cm². Afterthe ion injection, the resist R3 is removed.

(4) Then, as shown in FIG. 3D, a patterned resist R4 is formed, and afourth semiconductor region 34 of P type is formed by further injectingions in the second semiconductor region 32, using the resist R4 as amask. The ions to be injected may be, for example, boron (B⁺), the ioninjection energy may be, for example, 5 KeV-50 KeV, and the dopingamount may be, for example, 1.0×10¹³ atoms/cm²-1.0×10¹⁵ atoms/cm². Afterthe ion injection, the resist R4 is removed.

(5) Finally, as shown in FIG. 3E, a patterned resist R5 is formed, and athird semiconductor region 33 of N type is formed by further injectingions in the second semiconductor region 32, using the resist R5 as amask. The ions to be injected may be, for example, arsenic (As⁺), theion injection energy may be, for example, 10 KeV-100 KeV, and the dopingamount may be, for example, 1.0×10¹² atoms/cm²-1.0×10¹⁴ atoms/cm². Afterthe ion injection, the resist R5 is removed. The steps (1)-(5) describedabove may be conducted concurrently with formation of an electroniccircuit to be provided on the same silicon substrate 3.

Next, the angle restriction filter 10 is formed on the photodetectordevice 30 (see FIG. 2). For example, tungsten light shield members 13may be formed at the same time when forming conductive plugs forconnecting aluminum alloy layers for wiring for the above-describedelectronic circuit. Also, aluminum alloy layers 11 may be formed at thesame time when the aluminum alloy layers for wiring for theabove-described electronic circuit are formed. Silicon oxide layers 12may also be formed at the same time when forming dielectric filmsbetween the plural aluminum alloy layers for wiring for theabove-described electronic circuit. By a combination of thephotodetector device 30 and the angle restriction filter 10, an opticalsensor that detects incident light within a predetermined restrictionangle range (a directional optical sensor) can be obtained.

Next, a wavelength restriction filter 20 is formed on the anglerestriction filter 10 (see FIG. 2). For example, first, a silicon oxidelayer is formed on the angle restriction filter 10, and the siliconoxide layer is processed into a tilt structure 23 having a predeterminedangle by a CMP method or the like. Then, thin films of a lowerrefractive index 21 and thin films of a higher refractive index 22 arealternately laminated in multiple layers. The spectrum sensor 1 ismanufactured through the steps described above.

2. Second Embodiment

FIG. 4 is a see-through plan view of a photodetector device and aspectrum sensor in accordance with a second embodiment of the invention,and FIG. 5 is a cross-sectional view taken along lines V-V of FIG. 4.The spectrum sensor in accordance with the second embodiment isdifferent from the spectrum sensor in accordance with the firstembodiment mainly in terms of its photodetector device 40.

The photodetector device 40 in accordance with the second embodiment has(1) a first semiconductor region 41 of a first conductivity type that iselectrically connected to a first external electrode, and (2) a secondsemiconductor region 42 of a second conductivity type formed on thefirst semiconductor region 41, which are the same as the firstembodiment. The photodetector device 40 in accordance with the secondembodiment includes (3) a third semiconductor region 43 of the secondconductivity type that includes a second conductivity type impurityhigher in concentration than that of the second semiconductor region 42,and is formed on the second semiconductor region 42 and electricallyconnected to a second external electrode, and (4) a plurality of fourthsemiconductor regions (pinning layers) 44 of the first conductivity typeeach formed on the second semiconductor region 42 and surrounded by thethird semiconductor region 43, which are different from the firstembodiment.

In other words, in the first embodiment, the fourth semiconductorregions 34 of the second conductivity type are formed in plurality, eachsurrounded by the third semiconductor region (pinning layer) 33 of thefirst conductivity type. In contrast, in accordance with the secondembodiment, the fourth semiconductor regions (pinning layers) 44 of thefirst conductivity type are formed in plurality, each surrounded by thethird semiconductor region 43 of the second conductivity type.

The first semiconductor region 41 is connected to a connection section47 that connects to the first external electrode through the fifthsemiconductor region 45 of the first conductivity type. On the otherhand, the second semiconductor region 42 is connected to a connectionsection 48 connecting to a second external electrode at a portion 43 aoutside the light receiving region of the photodetector device 40through the third semiconductor region 43 (see FIG. 4) formed in alattice configuration along the light shield members 13 of the anglerestriction filter 10. Therefore, a reverse bias voltage can be appliedto a PN junction formed between the first semiconductor region 41 andthe second semiconductor region 42 through the first external electrodeand the second external electrode.

In accordance with the second embodiment, the fourth semiconductorregions (pinning layers) 44 of the first conductivity type are formed inplurality, each being surrounded by the third semiconductor region 43 ofthe second conductivity type, such that the fourth semiconductor regions44 can be secured in plurality on the second semiconductor region 42.Accordingly, generation of thermally excited carriers at the interfacebetween the silicon substrate 3 and the silicon oxide layer 12 andgeneration of dark current noise caused by the thermally excitedcarriers can be suppressed.

Furthermore, in accordance with the second embodiment, the fourthsemiconductor region 44 is surrounded by the third semiconductor region43 that is connected to the second external electrode (see FIG. 4), suchthat the distance in which carriers generated in the secondsemiconductor region 42 located below the fourth semiconductor region 44move to the third semiconductor region 43 can be shortened, and thus thecarriers are effectively moved.

Also, in accordance with the second embodiment, the plurality of thefourth semiconductor regions 44 are each connected to the connectionsection 49 connecting to the third external electrode. In the presentembodiment, as shown in FIG. 5, the connection section 47 to the firstexternal electrode and the connection section 49 to the third externalelectrode are connected through the angle restriction filter 10, suchthat the first external electrode and the third external electrode are acommonly shared electrode. By this structure, a voltage equivalent tothe above-described reverse bias voltage applied to the first externalelectrode can be applied to the plurality of the fourth semiconductorregions 44, such that a sufficient depletion layer can be formed in thesecond semiconductor region 42. It is noted that the pinning layers 44 ahaving the same impurity concentration as that of the fourthsemiconductor region 44 are connected to the first external electrodethrough the fifth semiconductor region 45. In this exemplary embodiment,the first external electrode and the third external electrode are acommonly shared electrode. However, without being limited to the above,the first external electrode and the third external electrode may havedifferent potentials in the same polarity.

In the first embodiment and the second embodiment described above, thefirst conductivity type is N type, and the second conductivity type andthe conductivity type of the silicon substrate 3 are P type. However,without being limited to the above, the first conductivity type may be Ptype, and the second conductivity type and the conductivity type of thesilicon substrate 3 may be N type. In this case, the first externalelectrode is an anode electrode, and the second external electrode is acathode electrode.

What is claimed is:
 1. A spectrum sensor comprising: a photodetectordevice; an angle restriction filter that transmits light incidentthereon in an incident angle range toward the photodetector device; anda wavelength restriction filter that restricts wavelengths of light thatpasses through the angle restriction filter, wherein the photodetectordevice includes: a first semiconductor region of a first conductivitytype electrically connected to a first connection section; a secondsemiconductor region of a second conductivity type formed on the firstsemiconductor region; a third semiconductor region of the firstconductivity type formed on the second semiconductor region; and aplurality of fourth semiconductor regions of the second conductivitytype formed on the second semiconductor region, each of the plurality offourth semiconductor regions being surrounded by the third semiconductorregion, each of the plurality of fourth semiconductor regions includinga second conductivity type impurity having a concentration higher than aconcentration of the second semiconductor region, and electricallyconnected to a second connection section.
 2. The spectrum sensoraccording to claim 1, wherein the third semiconductor region iselectrically connected to the first connection section.